You need to get yourself a good protien shake, its not essential but it will help maximise your gains. Most of all though it speeds up muscle recovery (give creatine ethyl ester capsules a go as well, you get them in sports nutrition shops)

As for diet, the best sources of protiens,fatty acids etc come from lean meat (and egg)so as long as your not lashing down burgers and mistery meat every day you'll be fine

As for carbs, pasta is good for energy as are oats because they are slow release carbs so you'll have energy for longer..sweet potatoes are excellent for this and make a nice change to jacket tatties

End of the day you dont need to be too anal about what you eat, just as long as you get a good mix of good and bad + strict diets are shite and only make you crave the things you cant have!

Also, if your after more size you'll need to be eating more than 2500cal a day...i'm currently on 4000 and its working well